Low Levels of a Neurotransmitter May Be Responsible for Cognitive Deficits in Patients with Schizophrenia

Low Levels of a Neurotransmitter May Be Responsible for Cognitive Deficits in Patients with Schizophrenia

The cognitive deficits that patients with schizophrenia are affected by, such as poor attention, memory, and problem-solving abilities, may correlate to decreased levels of a neurotransmitter in the brain, researchers at the University of California, Davis (UC Davis) have found.

Although the psychosis of schizophrenia is treated with antipsychotic medications, the cognitive impairments do not yet have a treatment, because the cause of the impairments had remained unknown. Now, the UC Davis researchers, led by Jong H. Yoon, assistant professor of psychiatry and behavioral sciences at UC Davis Health System and the study’s lead author, have discovered that a lack of the neurotransmitter gamma-aminobutyric acid, or GABA, in the brains of schizophrenic patients may be where the deficiency lies that causes the cognitive symptoms.

The study took place in two parts. First, Yoon and his colleagues measured GABA levels in the visual cortexes of the brains of 13 subjects with schizophrenia and 13 controls without the disorder. Using magnetic resonance spectroscopy, the researchers found that the schizophrenic patients had “a deficit in GABA of about 10 percent when compared with the non-schizophrenic controls.” In the next step, the researchers measured levels of visual perception, which revealed that the surround-suppression illusion the subjects were exposed to “had less of an effect on patients with schizophrenia, resulting in a highly unusual situation in which they outperformed healthy subjects when baseline differences in generalized task performance were accounted for.” The researchers determined that the low levels of GABA in patients were responsible for this behavioral abnormality.

“The link between changes in patients' brain chemistry and the cognitive impairments they experience never has been shown before in this way,” said Cameron Carter, professor of psychiatry and behavioral sciences, director of the Imaging Research Center and the study’s senior author. “This work provides tremendous support for targeting the GABA system for treatment of cognitive decline in schizophrenia.”